Relative reconstruction quality as a function of spectral separation for several levels of NCPA errors. The reconstruction quality is best for small spectral separations and small wavefront errors. The reconstruction quality converges at smaller spectral separations to the classic SCC quality. We see that the quality degrades when the NCPAs increase in strength, even for small spectral separations. The quality also degrades faster for large spectral separations than for small spectral separations. Both effects are due to higher-order terms that have been neglected in the small-phase approximation. A spectral separation smaller than 3% always show improvement.